Floating point operations are generally performed by specialized floating point hardware in the processor (CPU). If the floating point hardware is defective, however, floating point errors may lead to data corruption, and may not be detected for some time. Further, some floating point errors may be intermittent, and may be undetectable using standard diagnostic methods.
In the prior art, there exist different diagnostic methods for detecting floating point hardware failure. One method involves running diagnostic test applications from time to time. The execution result is then compared against the expected result. Floating point hardware failure is detected when there are differences in the results. One main problem with this diagnostic method is that a diagnostic test application, no matter how well designed, cannot exactly duplicate the floating point vectors produced by the user's application(s) and/or the kernel under real world circumstances. This is because the computer manufacturer cannot possibly predict and account for all possible types of user applications that may be developed for a given computer system. Accordingly, this diagnostic method may fail to detect floating point hardware failure for certain user applications.
Lockstep hardware represents another approach to detecting floating point hardware failure. The lockstep approach may involve, for example, having 2 processors run in a “lock step” fashion. In the lock step approach, the result from each CPU is compared with the other to ensure that they agree. If one CPU has an errant floating point unit, the comparison will fail and floating point hardware can thus be detected. However, the lockstep hardware approach is expensive as it involves hardware duplication. Furthermore, if both processors have identical problems (e.g., due to a defective design), the results produced will be identical, albeit erroneous, for certain floating point operations. In this case, the floating point hardware failure is not detectable using the lockstep hardware approach.